Trading in Hainan Airlines' shares had been suspended since January, as had shares in six other mainland-listed companies linked to Chinese conglomerate HNA which is under financing pressure following a $50 billion buying spree.

Its slump reflects ongoing investor jitters around HNA, whose opaque ownership structure and debt-fuelled acquisitions have sparked global regulatory scrutiny.

HNA-affliated CCOOP Group Co Ltd, which also resumed trading on Friday, similarly opened 10 percent lower, while Caissa Travel tumbled by the daily limit when it opened after a six-month halt on Thursday.

Hainan Airlines, China's fourth-largest airline which is also considered HNA's crown jewel, said in June that its owner would become Hainan Province Cihang Foundation, which is connected to HNA Group, after its restructuring.

It plans to issue shares to up to 10 investors to raise up to 7 billion yuan ($1 billion) to fund aircraft purchases and other projects, and is also buying aviation assets valued at 10.48 billion yuan.

(Reporting by Brenda Goh; Editing by Stephen Coates)